Monday, 3 July 2017

Ecological success and dominance

Evolutionary biology's best-known measure of success is fitness.
"Fitness" has become a popular term, and as a result of its success
it has become overloaded with multiple meanings - e.g. see
the 1982 Dawkins book chapter titled: "An agony in five fits".
Most definitions share the property that fitness measures
whether an entity - or a population of entities - is increasing in number.
"Fitness" usually measures the extent of that increase in some way.
From the perspective of ecology, fitness isn't the only success metric
in town - it just happens to be one that can be easily applied to individuals.
If broadening the perspective to include populations, one could also
consider the population size, its expected probability of going extinct
in some specified time, it rate of throwing off new distinct populations
and some measure of how well it is capturing and using resources.

The last concept is the one that this post is about. I think of it as
being "ecological success". Kudzu has it. Ants have it.
Islam has it. The decimal system has it. I think one reason this type of
metric is not more popular and better-known is that there's no consensus
regarding the best way to measure it. A thermodynamic metric seems
attractive to me: since resources can all (in principle) be manufactured
from available energy. Another possible metric involves weighing the
systems involved - to measure their mass. This is sometimes done when
measuring the extent to which humans have conquered the globe,
for example.

A sister concept is "ecological dominance". It refers to extreme
levels of success - where competitors are either obliterated or
marginalized.

These concepts can also be applied within particular niches. Entities
which are doing badly overall may be succeeding in or dominating their
particular niche.

If anything, attempting to apply these concepts to cultural evolution
is even harder than with organic systems.
Gene-meme coevolution results in entanglement in terms of gene and meme
products, which makes weighing them and calculating the energy flux
through them more challenging. The most common metrics used in cultural
evolution are a bit different. "Mindshare" is a common concept which is
used to measure cultural popularity within a cultural niche. Assuming that
a meme is either possessed by a host, or not, and assuming whether they
have it or not is measurable, the mindshare of a meme can be measured for
a given population. Another common metric that is used is US dollars.
Cultural products sometimes have monetary value, and
sometimes that can be calculated or estimated. However, some of the
most common memes are free. It seems as though these memes would be
unfairly disadvantaged by value-based metrics of popularity.
The internet has brought with it some other common popularity metrics:
views, links, clicks and likes. Unfortunately the supporting data is not
always publicly available. This data is beginning to be used by scientists.